Key slot



Dec. 29, 1931. G. T. JOHNSON KEY SLOT Filed June 6, 1928 Patented Dec. 29, 1931 UNETED STATES PATENT OFFICE GEORGE T. JOHNSON, OF COLUMBUS, OHIO, ASSIGNOR TO THE BUCKEYE STEEL CASTINGS COMPANY, OF COLUMBUS, OHIO KEY SLOT Application filed June 6,

This invention relates to the formation of the key slots now provided accordingto standard practice in draft yokes, car coupler shanks, and draft lugs. According to present practice, the slot and the key engaged therethrough are formed with parallel sides and with true semi-circular ends, the slot being somewhat wider than the key to provide necessary clearance for assembling. Un- 19 der these conditions, when the structure is first placed in service the bearing area between the edge of the key and the end wall of the slot is merely a line and a substantial bearing is not attained until either the key or the end wall of the slot is worn and deformed, and in many cases wear and deformation occurs in both the slot and the key. Because of the deformation, there is an accumulating slackness which is detrimeno tal to the proper functioning of the coupler or draft device. It is the object of my invention, therefore, to provide a slot of such formation that there is a substantial bearing area of contact between the key and the end of the slot when the parts are initially assembled, wear and deformation being consequently minimized. The object of the invention is attained in the manner indicated in the accompanying drawings and hereinafter set fOltll.

In the drawings, Figure 1 is a longitudinal section of a portion of a draft yoke having a slot therein;

Figures 2, 3, 4 and 5 are diagrammatic illustrations of various forms of slots embodying the present invention.

In order that the invention may be more readily comprehended, it is advantageous to specifically note the structure shown in Fig. 1 in which the reference numeral 1 indicates a portion of a draft yoke having a longitudinal slot 2 in each side, and 3 indicates a key engaged through the slots. It will be seen that the key and the slot both have straight parallel sides and semi-cylindrical ends which merge directly into the sides, and that the bearing contact between the key and the end wall of the slot is on the line 4: only so that considerable wear and deformation must occur in the slot or the key or both before a 1928. Serial No. 283,422.

substantial bearing surface will be attained.

According to the present invention, the end wall of the slot is formed through the greater portion of its extent on the same radius as the end of the key, as will be understood on reference to Fig. 2 in which 5 designates the key and 6 denotes the end wall of the slot. It will be noted that between the points 7 7 the curvature of the end wall of the slot coincides with the end of the key and the points 77 are close to the planes of the sides of the key so that a substantial bearing area is provided in the original production of the parts. In Fig. 2, the end wall of the slot extends from the points 7 on tangential lines 8 to the side walls to merge thereinto through short curves, as at 9, the bearing surface between the points 7-7 being nearly equal to the full width of the key. In Fig. 3, the area of contact is between the points 10-10 and is slightly greater than the area of contact in Fig. 2 while, instead of the straight tangential lines 8, curves 11 of wide radius connect the end wall with the side walls. In Fig. 4, the bearing area is between the points 1212 and is somewhat less than the area in Fig. 2 and Fig. 3 but is of suflicient extent to avoid rapid wear and deformation and the end wall of the slot is joined to the side walls through curves 13 of wide radius described about centres closer to the end of the key and the center line than are the centers of the curve 11.

In Fig. 5, the bearing area is very extensive, one boundary point 14.- being located at the junction of the curved end wall and one straight side wall while the other boundary point 14 is spaced from the other side wall but is connected therewith through a curve 15 of very wide radius, the clearance space 16 for relative play of the key and the side of the slot being all at one side in this embodiment of the invention.

It will be noted that in each form of the invention, the key is of less thickness than the the width of the slot, and that the radius of the curve at the end of the slot is less than half the width of the slot, and equal to the radius of the main curve at the edge of the key.

From the foregoing description, it will be seen that the objects of the invention are attained in a very simple manner without any increase in cost over the cost of production 5 of the form heretofore generally adopted. It will be understood that the invention is applied to both ends of the slot, and that while I have specifically mentioned a draft yoke the invention is to be embodied in any 10 draft member having a key-receiving slot. The arcuate bearing surface at the end of the slot is formed about the same center 1and with the same radius as the edge of the 15 Having fully described my invention what I claim as new and desire to secure by Letters-Patent, is

A key and slot construction having the end wall of the slot describing a pre-formed curve coincident with the pre-formed curvature of the end of the key through a substantial portion of its area the radius of said curve being less than half the width of the slot, and equal to half the thickness of the key.

In testimony whereof, I have signed this specification.

GEORGE T. JOHNSON. 

